[llvm] r264604 - Revert "[SimlifyCFG] Prevent passes from destroying canonical loop structure, especially for nested loops"
Reid Kleckner via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 28 11:07:41 PDT 2016
Author: rnk
Date: Mon Mar 28 13:07:40 2016
New Revision: 264604
URL: http://llvm.org/viewvc/llvm-project?rev=264604&view=rev
Log:
Revert "[SimlifyCFG] Prevent passes from destroying canonical loop structure, especially for nested loops"
This reverts commit r264596.
It does not compile.
Modified:
llvm/trunk/include/llvm/Transforms/Utils/Local.h
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll
llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll
llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll
llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll
Modified: llvm/trunk/include/llvm/Transforms/Utils/Local.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/Local.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/Local.h Mon Mar 28 13:07:40 2016
@@ -21,7 +21,6 @@
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Operator.h"
-#include "llvm/ADT/SmallPtrSet.h"
namespace llvm {
@@ -125,16 +124,13 @@ bool TryToSimplifyUncondBranchFromEmptyB
/// values, but instcombine orders them so it usually won't matter.
bool EliminateDuplicatePHINodes(BasicBlock *BB);
-/// This function is used to do simplification of a CFG. For
-/// example, it adjusts branches to branches to eliminate the extra hop, it
-/// eliminates unreachable basic blocks, and does other "peephole" optimization
-/// of the CFG. It returns true if a modification was made, possibly deleting
-/// the basic block that was pointed to. LoopHeaders is an optional input
-/// parameter, providing the set of loop header that SimplifyCFG should not
-/// eliminate.
+/// This function is used to do simplification of a CFG. For example, it
+/// adjusts branches to branches to eliminate the extra hop, it eliminates
+/// unreachable basic blocks, and does other "peephole" optimization of the CFG.
+/// It returns true if a modification was made, possibly deleting the basic
+/// block that was pointed to.
bool SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
- unsigned BonusInstThreshold, AssumptionCache *AC = nullptr,
- SmallPtrSetImpl<BasicBlock *> *LoopHeaders = nullptr);
+ unsigned BonusInstThreshold, AssumptionCache *AC = nullptr);
/// This function is used to flatten a CFG. For example, it uses parallel-and
/// and parallel-or mode to collapse if-conditions and merge if-regions with
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Mon Mar 28 13:07:40 2016
@@ -245,13 +245,10 @@ bool JumpThreading::runOnFunction(Functi
// Can't thread an unconditional jump, but if the block is "almost
// empty", we can replace uses of it with uses of the successor and make
// this dead.
- // We should not eliminate the loop header either, because eliminating
- // a loop header might later prevent LoopSimplify from transforming nested
- // loops into simplified form.
if (BI && BI->isUnconditional() &&
BB != &BB->getParent()->getEntryBlock() &&
// If the terminator is the only non-phi instruction, try to nuke it.
- BB->getFirstNonPHIOrDbg()->isTerminator() && !LoopHeaders.count(BB)) {
+ BB->getFirstNonPHIOrDbg()->isTerminator()) {
// Since TryToSimplifyUncondBranchFromEmptyBlock may delete the
// block, we have to make sure it isn't in the LoopHeaders set. We
// reinsert afterward if needed.
Modified: llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyCFGPass.cpp Mon Mar 28 13:07:40 2016
@@ -28,7 +28,6 @@
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/TargetTransformInfo.h"
-#include "llvm/Analysis/CFG.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constants.h"
@@ -131,20 +130,13 @@ static bool iterativelySimplifyCFG(Funct
AssumptionCache *AC,
unsigned BonusInstThreshold) {
bool Changed = false;
- bool LocalChange = true;
-
- SmallVector<std::pair<const BasicBlock *, const BasicBlock *>, 32> Edges;
- FindFunctionBackedges(F, Edges);
- SmallPtrSet<BasicBlock *, 16> LoopHeaders;
- for (unsigned i = 0, e = Edges.size(); i != e; ++i)
- LoopHeaders.insert(const_cast<BasicBlock *>(Edges[i].second));
-
+ bool LocalChange = true;
while (LocalChange) {
LocalChange = false;
// Loop over all of the basic blocks and remove them if they are unneeded.
for (Function::iterator BBIt = F.begin(); BBIt != F.end(); ) {
- if (SimplifyCFG(&*BBIt++, TTI, BonusInstThreshold, AC, &LoopHeaders)) {
+ if (SimplifyCFG(&*BBIt++, TTI, BonusInstThreshold, AC)) {
LocalChange = true;
++NumSimpl;
}
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon Mar 28 13:07:40 2016
@@ -135,7 +135,6 @@ class SimplifyCFGOpt {
const DataLayout &DL;
unsigned BonusInstThreshold;
AssumptionCache *AC;
- SmallPtrSetImpl<BasicBlock *> *LoopHeaders;
Value *isValueEqualityComparison(TerminatorInst *TI);
BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
std::vector<ValueEqualityComparisonCase> &Cases);
@@ -158,10 +157,8 @@ class SimplifyCFGOpt {
public:
SimplifyCFGOpt(const TargetTransformInfo &TTI, const DataLayout &DL,
- unsigned BonusInstThreshold, AssumptionCache *AC,
- SmallPtrSetImpl<BasicBlock *> *LoopHeaders)
- : TTI(TTI), DL(DL), BonusInstThreshold(BonusInstThreshold), AC(AC),
- LoopHeaders(LoopHeaders) {}
+ unsigned BonusInstThreshold, AssumptionCache *AC)
+ : TTI(TTI), DL(DL), BonusInstThreshold(BonusInstThreshold), AC(AC) {}
bool run(BasicBlock *BB);
};
}
@@ -3365,7 +3362,6 @@ bool SimplifyCFGOpt::SimplifySingleResum
// The landingpad is now unreachable. Zap it.
BB->eraseFromParent();
- if (LoopHeaders) LoopHeaders->erase(BB);
return true;
}
@@ -3484,7 +3480,6 @@ static bool removeEmptyCleanup(CleanupRe
// The cleanup pad is now unreachable. Zap it.
BB->eraseFromParent();
- if (LoopHeaders) LoopHeaders->erase(BB);
return true;
}
@@ -3565,11 +3560,9 @@ bool SimplifyCFGOpt::SimplifyReturn(Retu
}
// If we eliminated all predecessors of the block, delete the block now.
- if (pred_empty(BB)) {
+ if (pred_empty(BB))
// We know there are no successors, so just nuke the block.
BB->eraseFromParent();
- if (LoopHeaders) LoopHeaders->erase(BB);
- }
return true;
}
@@ -3726,7 +3719,6 @@ bool SimplifyCFGOpt::SimplifyUnreachable
BB != &BB->getParent()->getEntryBlock()) {
// We know there are no successors, so just nuke the block.
BB->eraseFromParent();
- if (LoopHeaders) LoopHeaders->erase(BB);
return true;
}
@@ -5070,14 +5062,8 @@ bool SimplifyCFGOpt::SimplifyUncondBranc
return true;
// If the Terminator is the only non-phi instruction, simplify the block.
- // if LoopHeader is provided, check if the block is a loop header
- // (This is for early invocations before loop simplify and vectorization
- // to keep canonical loop forms for nested loops.
- // These blocks can be eliminated when the pass is invoked later
- // in the back-end.)
BasicBlock::iterator I = BB->getFirstNonPHIOrDbg()->getIterator();
if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
- (!LoopHeaders || (LoopHeaders && !LoopHeaders->count(BB))) &&
TryToSimplifyUncondBranchFromEmptyBlock(BB))
return true;
@@ -5357,8 +5343,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB)
/// of the CFG. It returns true if a modification was made.
///
bool llvm::SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
- unsigned BonusInstThreshold, AssumptionCache *AC,
- SmallPtrSetImpl<BasicBlock *> *LoopHeaders) {
+ unsigned BonusInstThreshold, AssumptionCache *AC) {
return SimplifyCFGOpt(TTI, BB->getModule()->getDataLayout(),
- BonusInstThreshold, AC, LoopHeaders).run(BB);
+ BonusInstThreshold, AC).run(BB);
}
Modified: llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll (original)
+++ llvm/trunk/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll Mon Mar 28 13:07:40 2016
@@ -16,23 +16,23 @@ for.body:
%cmp1 = icmp eq i32 %a, 12345
br i1 %cmp1, label %if.then, label %if.else, !prof !0
; CHECK: %cmp1 = icmp eq i32 %a, 12345
-; CHECK-NEXT: br i1 %cmp1, label %for.body.us, label %for.body, !prof !0
+; CHECK-NEXT: br i1 %cmp1, label %if.then.us, label %if.else, !prof !0
if.then: ; preds = %for.body
-; CHECK: for.body.us:
+; CHECK: if.then.us:
; CHECK: add nsw i32 %{{.*}}, 123
; CHECK: %exitcond.us = icmp eq i32 %inc.us, %b
-; CHECK: br i1 %exitcond.us, label %for.cond.cleanup, label %for.body.us
+; CHECK: br i1 %exitcond.us, label %for.cond.cleanup, label %if.then.us
%add = add nsw i32 %add.i, 123
br label %for.inc
if.else: ; preds = %for.body
%mul = mul nsw i32 %mul.i, %b
br label %for.inc
-; CHECK: for.body:
+; CHECK: if.else:
; CHECK: %mul = mul nsw i32 %mul.i, %b
; CHECK: %inc = add nuw nsw i32 %inc.i, 1
; CHECK: %exitcond = icmp eq i32 %inc, %b
-; CHECK: br i1 %exitcond, label %for.cond.cleanup, label %for.body
+; CHECK: br i1 %exitcond, label %for.cond.cleanup, label %if.else
for.inc: ; preds = %if.then, %if.else
%mul.p = phi i32 [ %b, %if.then ], [ %mul, %if.else ]
%add.p = phi i32 [ %add, %if.then ], [ %a, %if.else ]
Modified: llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll (original)
+++ llvm/trunk/test/Transforms/LoopUnswitch/infinite-loop.ll Mon Mar 28 13:07:40 2016
@@ -16,10 +16,10 @@
; CHECK-NEXT: br i1 %a, label %entry.split, label %abort0.split
; CHECK: entry.split:
-; CHECK-NEXT: br i1 %b, label %for.body, label %abort1.split
+; CHECK-NEXT: br i1 %b, label %cond.end, label %abort1.split
-; CHECK: for.body:
-; CHECK-NEXT: br label %for.body
+; CHECK: cond.end:
+; CHECK-NEXT: br label %cond.end
; CHECK: abort0.split:
; CHECK-NEXT: call void @end0() [[NOR_NUW:#[0-9]+]]
Modified: llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/2008-05-16-PHIBlockMerge.ll Mon Mar 28 13:07:40 2016
@@ -1,6 +1,6 @@
; RUN: opt < %s -simplifycfg -S > %t
; RUN: not grep "^BB.tomerge" %t
-; RUN: grep "^BB.nomerge" %t | count 4
+; RUN: grep "^BB.nomerge" %t | count 2
; ModuleID = '<stdin>'
declare i1 @foo()
@@ -54,24 +54,24 @@ Exit: ; preds = %Succ
ret void
}
-; This function can't be merged (for keeping canonical loop structures)
+; This function can be merged
define void @c() {
entry:
- br label %BB.nomerge
+ br label %BB.tomerge
-BB.nomerge: ; preds = %Common, %entry
+BB.tomerge: ; preds = %Common, %entry
br label %Succ
Succ: ; preds = %Common, %BB.tomerge, %Pre-Exit
; This phi has identical values for Common and (through BB) Common,
; blocks can't be merged
- %b = phi i32 [ 1, %BB.nomerge ], [ 1, %Common ], [ 2, %Pre-Exit ]
+ %b = phi i32 [ 1, %BB.tomerge ], [ 1, %Common ], [ 2, %Pre-Exit ]
%conde = call i1 @foo( ) ; <i1> [#uses=1]
br i1 %conde, label %Common, label %Pre-Exit
Common: ; preds = %Succ
%cond = call i1 @foo( ) ; <i1> [#uses=1]
- br i1 %cond, label %BB.nomerge, label %Succ
+ br i1 %cond, label %BB.tomerge, label %Succ
Pre-Exit: ; preds = %Succ
; This adds a backedge, so the %b phi node gets a third branch and is
@@ -83,25 +83,25 @@ Exit: ; preds = %Pre-Exit
ret void
}
-; This function can't be merged (for keeping canonical loop structures)
+; This function can be merged
define void @d() {
entry:
- br label %BB.nomerge
+ br label %BB.tomerge
-BB.nomerge: ; preds = %Common, %entry
+BB.tomerge: ; preds = %Common, %entry
; This phi has a matching value (0) with below phi (0), so blocks
; can be merged.
%a = phi i32 [ 1, %entry ], [ 0, %Common ] ; <i32> [#uses=1]
br label %Succ
Succ: ; preds = %Common, %BB.tomerge
- %b = phi i32 [ %a, %BB.nomerge ], [ 0, %Common ] ; <i32> [#uses=0]
+ %b = phi i32 [ %a, %BB.tomerge ], [ 0, %Common ] ; <i32> [#uses=0]
%conde = call i1 @foo( ) ; <i1> [#uses=1]
br i1 %conde, label %Common, label %Exit
Common: ; preds = %Succ
%cond = call i1 @foo( ) ; <i1> [#uses=1]
- br i1 %cond, label %BB.nomerge, label %Succ
+ br i1 %cond, label %BB.tomerge, label %Succ
Exit: ; preds = %Succ
ret void
@@ -110,21 +110,21 @@ Exit: ; preds = %Succ
; This function can be merged
define void @e() {
entry:
- br label %Succ
+ br label %BB.tomerge
-Succ: ; preds = %Use, %entry
+BB.tomerge: ; preds = %Use, %entry
; This phi is used somewhere else than Succ, but this should not prevent
; merging this block
%a = phi i32 [ 1, %entry ], [ 0, %Use ] ; <i32> [#uses=1]
- br label %BB.tomerge
+ br label %Succ
-BB.tomerge: ; preds = %BB.tomerge
+Succ: ; preds = %BB.tomerge
%conde = call i1 @foo( ) ; <i1> [#uses=1]
br i1 %conde, label %Use, label %Exit
Use: ; preds = %Succ
%cond = call i1 @bar( i32 %a ) ; <i1> [#uses=1]
- br i1 %cond, label %Succ, label %Exit
+ br i1 %cond, label %BB.tomerge, label %Exit
Exit: ; preds = %Use, %Succ
ret void
Modified: llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll?rev=264604&r1=264603&r2=264604&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/EqualPHIEdgeBlockMerge.ll Mon Mar 28 13:07:40 2016
@@ -5,7 +5,7 @@
; RUN: not grep X: %t
; RUN: not grep 'switch i32[^U]+%U' %t
; RUN: not grep "^BB.tomerge" %t
-; RUN: grep "^BB.nomerge" %t | count 4
+; RUN: grep "^BB.nomerge" %t | count 2
;
; ModuleID = '<stdin>'
@@ -179,24 +179,24 @@ Exit: ; preds = %Succ
ret void
}
-; This function can't be merged (for keeping canonical loop structures)
+; This function can be merged
define void @c() {
entry:
- br label %BB.nomerge
+ br label %BB.tomerge
-BB.nomerge: ; preds = %Common, %entry
+BB.tomerge: ; preds = %Common, %entry
br label %Succ
Succ: ; preds = %Common, %BB.tomerge, %Pre-Exit
; This phi has identical values for Common and (through BB) Common,
; blocks can't be merged
- %b = phi i32 [ 1, %BB.nomerge ], [ 1, %Common ], [ 2, %Pre-Exit ]
+ %b = phi i32 [ 1, %BB.tomerge ], [ 1, %Common ], [ 2, %Pre-Exit ]
%conde = call i1 @foo( ) ; <i1> [#uses=1]
br i1 %conde, label %Common, label %Pre-Exit
Common: ; preds = %Succ
%cond = call i1 @foo( ) ; <i1> [#uses=1]
- br i1 %cond, label %BB.nomerge, label %Succ
+ br i1 %cond, label %BB.tomerge, label %Succ
Pre-Exit: ; preds = %Succ
; This adds a backedge, so the %b phi node gets a third branch and is
@@ -208,25 +208,25 @@ Exit: ; preds = %Pre-Exit
ret void
}
-; This function can't be merged (for keeping canonical loop structures)
+; This function can be merged
define void @d() {
entry:
- br label %BB.nomerge
+ br label %BB.tomerge
-BB.nomerge: ; preds = %Common, %entry
+BB.tomerge: ; preds = %Common, %entry
; This phi has a matching value (0) with below phi (0), so blocks
; can be merged.
%a = phi i32 [ 1, %entry ], [ 0, %Common ] ; <i32> [#uses=1]
br label %Succ
Succ: ; preds = %Common, %BB.tomerge
- %b = phi i32 [ %a, %BB.nomerge ], [ 0, %Common ] ; <i32> [#uses=0]
+ %b = phi i32 [ %a, %BB.tomerge ], [ 0, %Common ] ; <i32> [#uses=0]
%conde = call i1 @foo( ) ; <i1> [#uses=1]
br i1 %conde, label %Common, label %Exit
Common: ; preds = %Succ
%cond = call i1 @foo( ) ; <i1> [#uses=1]
- br i1 %cond, label %BB.nomerge, label %Succ
+ br i1 %cond, label %BB.tomerge, label %Succ
Exit: ; preds = %Succ
ret void
@@ -235,21 +235,21 @@ Exit: ; preds = %Succ
; This function can be merged
define void @e() {
entry:
- br label %Succ
+ br label %BB.tomerge
-Succ: ; preds = %Use, %entry
+BB.tomerge: ; preds = %Use, %entry
; This phi is used somewhere else than Succ, but this should not prevent
; merging this block
%a = phi i32 [ 1, %entry ], [ 0, %Use ] ; <i32> [#uses=1]
- br label %BB.tomerge
+ br label %Succ
-BB.tomerge: ; preds = %Succ
+Succ: ; preds = %BB.tomerge
%conde = call i1 @foo( ) ; <i1> [#uses=1]
br i1 %conde, label %Use, label %Exit
Use: ; preds = %Succ
%cond = call i1 @bar( i32 %a ) ; <i1> [#uses=1]
- br i1 %cond, label %Succ, label %Exit
+ br i1 %cond, label %BB.tomerge, label %Exit
Exit: ; preds = %Use, %Succ
ret void
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